In the construction of integrated circuit structures, device geometries are constantly shrinking, resulting in an increase in parasitic capacitance between devices. This includes increases in parasitic capacitance between adjacent metal interconnects, either on the same layer or between adjacent metal interconnect layers, which can result in crosstalk between the metal lines or interconnects and in a reduction of the response time. Lowering the capacitance between metal interconnects separated by dielectric material can be accomplished by either increasing the thickness of the dielectric material or by lowering the dielectric constant of the dielectric material. Increasing the thickness of the dielectric materials is, however, contrary to the goal of reducing device and structure geometries.
As a result, to reduce the parasitic capacitance between metal interconnects on the same or adjacent layers, one must change the material used between the metal lines or interconnects to a material having a lower dielectric constant than the materials currently used, i.e., silicon dioxide (SiO.sub.2).
Jeng et al. in "A Planarized Multilevel Interconnect Scheme with Embedded Low-Dielectric-Constant Polymers for Sub-Quarter-Micron Applications", published in the Journal of Vacuum and Technology in June 1995, discuss the use of a low dielectric constant polymeric material, such as parylene, as a substitute for silicon dioxide (SiO.sub.2) between tightly spaced conductor lines or other strategically important areas of an integrated circuit structure.
Parylene, a generic name for thermoplastic polymers based on p-xylylene monomers, has been shown to possess suitable physical, chemical, electrical, and thermal properties. Formation and deposition of such polymers by the initial decomposition of a stable dimer, followed by deposition and polymerization of the resulting reactive monomer, is discussed by Ashok K. Sharma in "Parylene-C at Subambient Temperatures", published in the Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 26, at pages 2953-2971 (1988). Properties of such polymeric materials, including their low dielectric constants, are further discussed by R. Olson in "Xylylene Polymers", published in the Encyclopedia of Polymer Science and Engineering, Volume 17, Second Edition, at pages 990-1024 (1989).
However, changing the dielectric material in the construction of integrated circuit structures from conventional silicon dioxide (SiO.sub.2) to polymeric materials cannot be accomplished using conventional methods and apparatus used to form SiO.sub.2 dielectric materials between adjacent metal lines or interconnects on a single layer or between adjacent layers of metal interconnects.